1. Field of the Invention
The present invention relates to a vertical light emitting type backlight module, which provides an image by directly emitting light from the underneath of an LED (Light Emitting Diode) panel, and more particularly to a vertical light emitting type backlight module of a liquid crystal display, which has reduced change of path of light, thereby decreasing light loss, while having a simplified lens structure, thereby allowing easy manufacturing and design.
2. Description of the Related Art
As a current developing trend in the electronic equipment industry, LCDs (Liquid Crystal Display) have been spotlighted as next generation display devices. However, since LCDs do not emit light on their own, an LCD panel for communication is provided, at the rear side thereof, with a backlight for emitting light.
The backlight enables colors of an image realized by the LCD panel to be reproduced nearly into real colors by emitting white light from the rear side of the LCD panel. As for the light source of the backlight, in the early days of the backlight, a CCFL (Cold Cathode Fluorescent Lamp) or an EEFL (External Electrode Fluorescent Lamp) was used. However, with the advent of highly efficient LEDs (Light Emitting Diode) having excellent physical and chemical properties, it has been suggested to employ LEDs as the light source for the backlight.
As for the backlight module employing the LED, there are a direct illumination type backlight module, which emits the light directly under the LCD panel, and a side emitting type backlight module, which is formed, at one side of the backlight module, with the light source, so that the light path is changed to direct light to the front side thereof using a reflection plate or a light guide plate.
The LED is a semiconductor light emitting device, which emits various colors of light, with the light source being constituted by compound semiconductors of various materials, such as GaAs, AlGaAs, GaN, InGaN and AlGaInP. As a standard for determining characteristics of the LED, colors, brightness, intensity of light, and the like, are used, and these are determined primarily by the compound semiconductor material used for the LED, and secondarily by the structure of the package for mounting LED chips. Accordingly, the package may have various structures according to requirements for applications of the LED.
FIG. 1 is a cross-sectional view illustrating an LED device suggested as a light source for a conventional side emitting type LCD backlight module. The LED device 10 comprises a lead line 12 for inputting or outputting an electrical signal, a package 11 made of a plastic material and being provided with a thermally conductive material therein, an LED chip 14 mounted in the package 11, and a lens 13 coupled to the package 11 on the top surface of the package 11 for changing the path of light generated from the LED chip 14 to the horizontal direction.
The lens 13 is optically designed such that respective light generated from the LED chip 14 and emitted in every direction may be refracted in the horizontal direction. Although the lens has a mortar-like shape in FIG. 1, there are problems in that, according to the emitting angle of the light generated from the LED chip 14, the lens may be more complicated, and in that the light deviated from ranges corresponding to an optical design thereof can be directed in the vertical direction without being refracted in the horizontal direction.
Additionally, when using the LED device 10 to realize the LCD backlight module, as shown in FIG. 2, the LED devices 10, each acting as a spot light source, are mounted in a line on a printed circuit substrate 21 having a predetermined length, thereby forming an LED array module 20 acting as a linear light source. Then, as shown in FIG. 3, after one or more LED array modules 20 are arranged in parallel and spaced predetermined distance apart, Each of the LED array modules 20 is provided, at either side of the LED array module 20, with a reflection plate 31 adapted to reflect the light emitted from the LED array module 20 in the horizontal direction to the vertical direction, thereby providing a backlight module 30.
As described above, with the backlight module 30 employing the conventional LED, the light initially generated by the LED chip 14 practically used as the light source is refracted in the horizontal direction by the lens 13, and is then reflected in the vertical direction by the reflection plate 31, whereby the path of the light is changed several times. As a result, there are several problems in that, firstly, the lens has a complicated structure in order to reflect the light generated by the LED chip 14 in the horizontal direction, thereby complicating the design and the manufacturing, in that, secondly, while initially generated light is forced to follow the path of the light changed several times, light loss can occur, in that, thirdly, when the light is refracted using the differences in refraction rates, since the light generated from the center of the LED device in a direction of an upper portion of the LED device is transmitted without having its direction changed, there can occur a hot spot at the center of the LED device, thereby requiring a shadow sheet for the backlight module 30 in order to prevent the hot spot from being generated.